The highest gust that occurred between 00 UTC on Monday and 07 UTC this morning from Ophelia was 96 mph at Roches Point on the south coast of Ireland, and occurred at 11 UTC (fig 1).
And just for completeness here are all the low-level stations that reported storm force gusts at anytime during that same period (fig 2).
On the face of it the warnings issued for the winds from ex-hurricane Ophelia look like they did there job, and that although three people died in Ireland, the warning saved many more, and that might well be true. But what about the accuracy of the warnings issued by both Met Eireann and the Met Office?
If you remember Met Eireann amended their status Red and Amber warnings at around 9 am on Monday morning. They jumped the highest gusts expected from 80 mph to 93 mph, and extended the status Red to cover the entire country. If we look at the maximum gusts across Ireland in more detail (fig 3) you will see that the first warning they issued on Saturday for maximum gusts to 80 mph would have sufficed for all stations bar Roches Point, even across the north of Ireland all the gusts from the observing network were within the range of 50 to 80 mph stipulated in the original warning. The one thing that was wrong with Saturdays warning is that it didn’t single out the south coast as particularly vulnerable to the storm force southerly winds from Ophelia, especially the county of Cork which saw the highest gusts in excess of 90 mph. I’m not going to say whether the status red for the entire country was not warranted because I would likely put my foot right in it.
Lets remind ourselves what the Met Office were warning us about as regards strong winds from Ophelia for the 16th in the UK.
Well as we’ve seen already the highest gust across Northern Ireland was 63 mph and did fall in the 55-65 mph range mentioned in the warning, but gusts in the range 65 to 75 mph or even 80 never occurred. And there lies the rub, because it’s never entirely clear from any warning issued by the Met Office what limits they use for yellow, amber or red warnings, and the reason why they don’t specify them is because it makes them impossible to verify. There is little doubt that the core of the strongest wind was along the south coast of Ireland, and up through the Irish Sea, in fact three stations in the northwest of Wales reported gusts of higher than 80 mph, and two of those, Aberdaron and Capel Curig reported gusts of 90 mph.
So using gusts of 70 mph or more as the basis for delineating the area of an amber warning, what should the area have looked like for the UK? Well on the basis of the wind speeds from the SYNOP stations it certainly wouldn’t have covered Northern Ireland, but instead stretched in an arc from Islay in the north down the Irish Sea possibly as far down as South Wales in the south (fig 6).
Looking back at the graphic from the NHC from Friday which shows the wind speed probabilities for Monday it shows look remarkably accurate. If the axis of the core of strongest winds had been aligned a little bit further east then it would have been spot on (fig 7). Perhaps we ought to leave it to the NHC to issue the warnings the next time a ex-hurricane heads our way.